1. Field of the Invention
The present invention relates generally to the field of refrigeration, and specifically to those systems which operate to serve a refrigeration load such as a water chiller or direct expansion coil, and also to provide a source of heated liquid. Such systems are sometimes referred to as "heat recovery" systems. The present invention addresses itself to systems of this type wherein an air cooled condenser is utilized in addition to the liquid cooled condenser which provides the source of heated liquid.
2. Description of the Prior Art
The only prior art known to applicant which discloses a refrigeration system having both an air cooled condenser and a liquid cooled heat recovery condenser is U.S. Pat. No. 3,188,829. In this system, the liquid cooled condenser and air cooled condenser are in series flow relationship such that all refrigerant flowing in the system passes through both condensers, without condensed refrigerant level control for the liquid cooled condenser. Further, the fan provided for forcing air in heat exchange relationship with the air cooled condenser does not include any means for controlling its capacity when there is a demand for heated liquid from the liquid cooled condenser.
U.S. Pat. No. 2,787,128 discloses a refrigeration system which includes a first liquid cooled condenser and a second liquid cooled heat recovery condenser. In this system, the two condensers are connected in parallel flow relationship and means are provided for restricting the flow of cooling water to the first condenser during those times that a demand for heated liquid from the heat recovery condenser exists, thereby increasing the operating pressure within said condensers in order to provide hot liquid of a desired temperature.
U.S. Pat. No. 3,916,638 discloses another refrigeration system having two liquid cooled condensers, one of which is adapted for heat recovery. In this system, the heat recovery condenser may be taken out of the refrigerant flow circuit through the actuation of appropriate valve means such that, during those times when there is no demand for heated liquid the refrigerant does not flow through the heat recovery condenser. When such demand exists, however, the condensers are in series flow relationship such that all refrigerant in the system must flow through both condensers.